It is well known in the electronic arts to make connections to semiconductor devices and integrated circuits and the like, by bonding of thin wires to bonding pads provided on these devices. Gold, aluminum, copper and alloys thereof are examples of materials which are commonly used for bonding pads and/or for connecting wires.
A well known method for attaching wires to bonding pads on semiconductor devices and the like is by thermo-compression bonding. In a typical arrangement, a thin wire of, for example, gold or aluminum, is captured between the bonding pad to which attachment is to be made and a bonding wedge. Pressure is applied to the bonding wedge to partially compress the captured wire and the bonding wedge is rapidly scrubbed back and forth, usually using ultrasonic energy. The combination of pressure and the heat generated by the scrubbing produces a weld between the wire and the bonding pad. During the bonding process, the portion of the wire captured between the bonding wedge and the bonding pad is substantially flattened.
For certain types of devices, as for example RF transistors or integrated circuits, it is necessary to provide many closely spaced parallel wire connections between the bonding regions on the device and the bonding regions on leadframe or circuit board on which the device is mounted. Often, the connecting wires must be bonded to the device and to the board or leadframe so that they have carefully controlled predetermined loop heights and spacings. This is because, at the frequencies at which many RF devices operate, the length, curvature, and spatial relationship between the bonding wires and the rest of the circuit exerts a substantial influence on the parasitic inductance and capacitance. Parasitic inductance and capacitance of the interconnections can have a profound effect on overall performance. Thus, in fabricating such RF devices and circuits, it is very important to be able to provide evenly spaced uniform wire bonds.
As device sizes are reduced the wires must be even more closely spaced and small deviations in wire spacing and/or alignment become electrically more significant. Also, as the speed of bonding and the degree of automation associated with the bonding process increase, it becomes progressively more difficult to achieve consistent, parallel, multiple, closelyspaced wire bonds. Accordingly, a need continues to exist for improved means and methods for wirebonding which permit one to obtain very evenly spaced uniform wire bonds having extremely well controlled wire loop size and orientation, particularly when a large number of closely spaced wires and wire bonds must be utilized.